The present invention relates in general to filament winders and in particular to a new and useful winding system which utilizes a robot arm to index a winding head at selected locations around a fixed mandrel, for winding the mandrel with filament in a selected and, if desired, complex pattern.
Various configurations for a winding head which is useful in winding filaments or fibers around a mandrel are known. Examples can be found in U.S. Pat. Nos. 3,701,489 and 3,741,489.
U.S. Pat. No. 4,145,740 is also relevant for its showing of a controllable winding head.
Substantially all other prior art winders require some movement on the part of the mandrel to be wound, in addition to movements of the winding head.
A comprehensive discussion of filament winders can be found in the course notes for a course entitled "Composites in Machine Element" given by Dr. G. D'Andrea at RPI in Troy, N.Y.
Among the simplest winders utilizes a mandrel which is mounted for rotation about its axis and a winding head for supplying a filament that is slidably movable parallel to the axis and next to the mandrel. A helical winding pattern can be established on the mandrel by moving the winding head back and forth. A mandrel can also be wound with the winding head moving slowlin in one direction along the rotatational axis of the mandrel. This is known as circumferential or hoop winding.
Polar winders are known which rotate the mandrel on an axis which is perpendicular to the longitudinal axis of the mandrel. A filament can then be wound in a direction which is at a small angle to the axis of the mandrel and from end to end around the mandrel until the mandrel is covered.
A continuous helical winding of a mandrel can be achieved by rotating the mandrel about its longitudinal axis and, at the same time, moving the mandrel parallel to its longitudinal axis. One or more fixed winding heads can be provided for supplying filament to the periphery of the mandrel. In this way, a mandrel which is being extruded from a forming machine can be helically wound with a filament or ribbon.
In addition to the foregoing helically wound filament or ribbon, an axially extending ribbon can be provided to the surface of the mandrel before it is wound also in a helical direction.
A continuous rotating mandrel can also be utilized for a helical winding and is known as a Drostholm wrap. In this process the mandrel rotates and the filaments are added from a stationary reel which is at a slight angle to a direction perpendicular to the axis of the mandrel. The wrap advances axially and helically on the mandrel.
Fiber-placement machines are also known which can produce a more complicated winding pattern for a fiber or filament. Such devices are useful when utilizing costly boron fiberepoxy tapes for filament winding. Such tapes are utilized to increase the strength of a mandrel that is usually adapted for high speed rotation, such as a flywheel or helicopter rotor hub.
Such devices can lay down tape in the X,Y and Z coordinates. Such machines generally require a tape dispenser which has 6.degree. of freedom and is capable of placing tape within plus or minus 0.01 inches of a desired path. Considerable expense and some problems have been encountered in such devices however. Such devices are particularly useful in the aircraft and aerospace industries which have begun to utilize high strength continuous filaments to reinforce various structural elements.
In addition to the foregoing known winders, loop-wrap winders are known which place filaments into loops for products such as tension straps for guy lines.
Braid-wrap winders supply a plurality of filaments or tapes which are wrapped, in maypole fashion over a mandrel which can, for example, be made of plastic, glass or other material which requires reinforcement.
Inside-wrap winders are also known. These utilize a process wherein filaments of reinforcing material are applied in a programmed manner to the inside of a rotating mandrel.
Tumbling-type machines are also utilized which move a mandrel in a complex tumbling path. This is used in conjunction with a fixed filament supply head for placing strands of the fiber one next to the other around the mandrel.
Planetary winding machines are also utilized having a support which carries a fiber supplying eye and also a spool of fiber. The support is rotated around the mandrel which itself is also rotated to wrap and cover the mandrel with fiber. Such winders are particularly useful in winding spherical or spheroid mandrels.
Finally, a winding process known as the Strickland B winding process utilizes a conical mandrel which can be rotated both about its longitudinal axis and on an axis transverse to its longitudinal axis, in conjunction with a winding head which can be moved parallel to the axis of the conical mandrel. By using such a device both radial and longitudinal windings of the conical surface can be achieved.
As previously noted, substantially the known winding techniques utilize some motion of the mandrel. The techniques are also similar in that mandrels are generally symmetrical at least about one axis.
The benefits of using high modulus, low density composites in structural applications have resulted in innovations which utilize reinforced plastics in the aerospace, automotive and energy related industries. Such industries utilize structural elements which are often quite complex in shape and cannot easily be wound by known winding techniques and devices. This is despite the fact that such complex structures can be strengthened drastically by the use of filament windings or maintaining low weight for such structures.